This invention relates generally to waste pyrolysis, and more specifically to, movement of drums of waste materials through a pyrolysis system.
Several drum processing applications, for example, those which include pyrolysis of waste material in drums, subject the drums or the contents of the drums to an environment containing inert or reactive gasses, high or low temperatures, high pressure liquid washing, or radiation in combination with these conditions. Certain of these drum processing applications involve transportation of the drums through extremely dirty and dusty environments. Many of these drum processing applications utilize a high reliability seal between a processing tunnel and a drum transporter drive mechanism. As used herein, a drum is considered to be a container for holding waste, for example, a 55 gallon barrel. Pyrolysis, as used herein, is a decomposition or transformation of a compound caused by heat.
For cleaner, milder temperature, and non-corrosive gas drum processing applications, it is sufficient to use standard roller conveyers, moving conveyor belts, or chains. In other applications, steel cables are utilized to move drums through processing tunnels. Unfortunately, in the drum processing applications described above, (i.e. those involving highly destructive or corrosive gasses and/or extremes in temperature) the environmental conditions cause such devices to be highly unreliable or infeasible. Conveyor belts and roller conveyor type devices are not suitable because they jam up when covered with dust. Conveyor belts and roller conveyor type devices also impede heat transfer to drum bottoms or a liquid to be sprayed onto the drum bottoms. Rubber, fabric or polymer belts cannot withstand high temperatures and aggressive gasses. Metallic belts contain many moving parts, which erode, corrode, jam and break. It is also difficult to load drums on and off such belts. In addition the drums can slip on the belts causing jam-ups and costly removal and repair of the whole conveyor unit. Linked metallic belts having lugs to hold the drums reduce this problem, but further increase cost and complexity, and do not diminish problems associated with many moving parts.
Further, drum transport systems such as belts, rollers, or chains typically utilize a horizontal access port in a side of the processing tunnel. Such transport systems have to utilize additional actuators located inside the tunnel to move drums into position on the belt, chain or rollers, for example, an additional belt, roller, or chain transport system. However, actuators inside the tunnel are prone to failure due to the harsh environmental conditions, for example, those conditions found in a pyrolysis system. Lastly, all of these drum transport mechanisms utilize complicated tensioning devices to compensate for large extremes in temperature as which are present within pyrolysis systems.
Drum transporting systems which utilize a cable system could also be used. These cable systems are built with rigid metal bars attached to two horizontally spaced moving cables so that drums between the metal bars are moved along in a line. Unfortunately thermal flexing of the cables is a source of wear and degradation. Additionally, the use of cables typically results in the use of complicated tensioning devices to compensate for the wide temperature extremes associated with a chamber of a pyrolysis system. When the tensioning devices are located outside the pyrolysis chamber, a complicated and failure prone gas seal must be used to allow movement of the drum transport mechanisms. This seal is normally at the same high temperatures as the pyrolysis chamber. Finally, most materials available for constructing flexible cables are not suitable for use in a high temperature pyrolysis environment. For example, stainless steel, which contains nickel, becomes corroded by sulfur contact at 1200 degrees Fahrenheit, making it unsuitable for cable construction.
In addition, horizontal drum transport devices such as belts, rollers, chains, cables, or trolleys, only apply force to the drum at one location, which is usually at the bottom of the drum. In such cases, the drums could easily tip over if small horizontal forces opposite the force of the drum transport device are applied to the top of the drum. In certain known pyrolysis systems, carbonaceous accumulations on the walls or ceiling of the pyrolysis chamber can cause such undesirable and costly tipping.